<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <title>Title</title>
    <link rel="stylesheet" type="text/css" href="https://cdn.bootcss.com/twitter-bootstrap/4.1.3/css/bootstrap.css">
    <link rel="stylesheet" type="text/css" href="./css/my.css">
    <script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.js" type="text/javascript"></script>
    <script src="https://cdn.bootcss.com/twitter-bootstrap/4.1.3/js/bootstrap.bundle.js" type="text/javascript"></script>
</head>
<body>
<div class="container">
    <div class="row justify-content-md-center">
        <div class="col col-lg-2">
            1 of 3
        </div>
        <div class="col-md-auto">
            Variable width content
        </div>
        <div class="col col-lg-2">
            3 of 3
        </div>
    </div>
    <div class="row">
        <div class="col">
            1 of 3
        </div>
        <div class="col-md-auto">
            Variable width content
        </div>
        <div class="col col-lg-2">
            3 of 3
        </div>
    </div>
</div>
</body>
</html>